The invention relates generally to product coding and marking operations, and more particularly to systems and methods for transferring print from a ribbon onto a substrate with a bi-directionally movable print head, and for advancing the ribbon and for braking advancement thereof with a bi-directional rotary drive member.
Thermal printing systems are employed widely for printing variable information on products and packaging in coding and marking operations. Many thermal printing systems include, for example, an inked ribbon or foil supplied from an unwind reel, between a thermal print head and a substrate, and then to a rewind reel. The ribbon is usually drawn intermittently under tension from the unwind reel by the rewind reel or by a ribbon feed roller, and the thermal print head is swept along a backside of the ribbon to transfer ink therefrom onto a target area of the substrate. More particularly, the thermal print head generally sweeps laterally, starting from a home position, along the backside of the ribbon in a direction opposite the ribbon feed direction so that the ribbon is held taut by the rewind reel or the feed roller during printing. After printing, the print head is sometimes moved away from the ribbon and is generally swept laterally back to the home position for the next print sweep.
In high production coding and marking operations, it is desirable generally to feed product or packaging to a print position opposite the print head as quickly as possible. In many such operations, however, the product or packaging can be fed to the print position more quickly than the print head can be moved back to the home position for the next print sweep. In these operations it is desirable to program the print head to print bi-directionally, thereby eliminating any delay associated with repositioning the print head. But when printing in the same direction as the ribbon feed direction, as will occur when printing bi-directionally, the ribbon has a tendency to form slack, which will prevent proper ink transfer, likely waste ribbon, and possibly jam the printer.
Also, many coding and marking printer systems are operated pneumatically, including, among other operational aspects, actuation of the thermal print head as disclosed in European Patent Publication No. EP 0,683,055 entitled "Economic Use of Impression Transfer Material Printing Method" published Nov. 22, 1995 in the name of Prestek Limited. Recently, however, there has been a trend in the manufacturing and packaging industries to eliminate from their facilities compressed air supply systems, which increases infrastructure, operational and maintenance costs. Also, usage of compressed air is very often a source of product contamination, particularly in the food processing and packaging industries. It is thus desirable to replace pneumatically operated coding and marking systems with all electrical systems, which are less costly and less problematic.
The present invention is drawn toward advancements in the art of transferring ink from a ribbon onto a substrate with a bi-directional thermal print head, and for advancing ribbon and braking advancement thereof with a bi-directional rotary drive member.
It is thus an object of the present invention to provide novel methods and systems for transferring print from a ribbon onto a substrate with a system that overcomes problems in the prior art.
It is a more particular object of the invention to provide novel methods and systems for printing bi-directionally with a thermal print head movable back and forth along a print path adjacent a ribbon to transfer ink therefrom onto a substrate. The ribbon being drawn from an unwind reel and adjacent the print path in the first direction of the print head, and the ribbon being clamped against a fixed ribbon guide to maintain tension on the ribbon at least when the print head moves in the same direction as ribbon is drawn along the print path. It is a related object of the invention to maintain tension on the ribbon with a rewind reel, which is rotatable in only one direction to draw ribbon from the unwind reel, when the print head moves in the second direction along the print path.
It is more particular related object of the invention to provide novel methods and systems for rotating a bi-directionally rotatable rotary drive member in a first direction to actuate a brake member that clamps the ribbon against a fixed ribbon guide, and rotating the rotary drive member in a second opposing direction to rotate the rewind reel to draw ribbon from the unwind reel.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.